Russia appears to have deployed special forces to an airbase in western Egypt near the border with Libya in recent days, U.S., Egyptian and diplomatic sources say, a move that would add to U.S. concerns about Moscow’s deepening role in Libya.

The U.S. and diplomatic officials said any such Russian deployment might be part of a bid to support Libyan military commander Khalifa Haftar, who suffered a setback with an attack on March 3 by the Benghazi Defence Brigades (BDB) on oil ports controlled by his forces.

The U.S. officials, who spoke on condition of anonymity, said the United States has observed what appeared to be Russian special operations forces and drones at Sidi Barrani, about 60 miles (100 km) from the Egypt-Libya border.

Egyptian security sources offered more detail, describing a 22-member Russian special forces unit, but declined to discuss its mission. They added that Russia also used another Egyptian base farther east in Marsa Matrouh in early February.